WDPN31 PGTW 050900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (MUN) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 31.1N 147.1E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 351 NM NORTHEAST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: EASTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS OF DEEP CONVECTION TIGHTLY WRAPPING INTO THE LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL STORM (TS) 04W (MUN). THE SYSTEM IS COMPACT, WITH CONVECTION MAINLY SPREAD ACROSS THE SOUTHERN SEMICIRCLE. ENVIRONMENTAL ANALYSIS REVEALS CLOUD TOP TEMPERATURES BETWEEN -62 AND -72 DEGREES C. ADDITIONALLY, TS 04W IS IN OVERALL FAVORABLE CONDITIONS FOR FURTHER INTENSIFICATION, AS INDICATED BY WARM (27-28 C) SEA SURFACE TEMPERATURES (SST), LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) AND MODERATE OUTFLOW ALOFT. THE CORE OF THE SYSTEM REMAINS MOIST, HOWEVER SIGNIFICANTLY DRIER AIR IS SURROUNDING THE CIRCULATION AND IS EXPECTED TO BEGIN IMPACTING THE STRUCTURE OF THE VORTEX. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE ANIMATED VISIBLE SATELLITE IMAGERY SHOWING A PARTIALLY EXPOSED LLCC IN THE CENTER OF THE ASSOCIATED DEEP CONVECTIVE BANDING. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE ESTIMATES LISTED BELOW, IN CONJUNCTION WITH THE COMPACT STRUCTURE OF THE SYSTEM. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH AND SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS KNES: T3.5 - 55 KTS CIMSS SATCON: 56 KTS AT 050312Z CIMSS ADT: 41 KTS AT 050530Z CIMSS AIDT: 56 KTS AT 050530Z CIMSS D-MINT: 45 KTS AT 050312Z CIMSS D-PRINT: 41 KTS AT 050600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD OTHER FACTORS: DRY AIR SURROUNDING THE SYSTEM ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 04W IS FORECAST TO TRACK EAST-NORTHEASTWARD OVER THE NEXT 24-36 HOURS, UNDER THE PREDOMINANT INFLUENCE OF A STR TO THE SOUTH. AFTERWARD, RIDGING WILL BUILD TO THE EAST, RESULTING IN STEERING THE SYSTEM NORTHWESTWARD AND EVENTUALLY NORTHEASTWARD. IN TERMS OF INTENSITY, TS 04W IS FORECAST TO REACH PEAK INTENSITY OF 60- 65 KTS WITHIN THE NEXT 12-24 HOURS. AFTER THAT, RAPIDLY COOLING SST, AS WELL AS INCREASING DRY AIR ENTRAINMENT WILL RESULTS IN WEAKENING. AROUND TAU 72, THE SYSTEM WILL BEGIN ITS SUBTROPICAL TRANSITION, WHICH IS EXPECTED TO BE COMPLETED BY OR BEFORE THE END OF THE CURRENT FORECAST PERIOD. MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN FAIR AGREEMENT, WITH CROSS-TRACK SPREAD OF JUST 25 NM AT TAU 36, EXPANDING HOWEVER TO OVER 250 AT TAU 72, INDICATING UNCERTAINTY IN HOW DIFFERENT MODELS IDENTIFY THE INTERACTION BETWEEN THE SYSTEM AND THE BUILDING RIDGE TO THE EAST, AS WELL AS THE BAROCLINIC ZONE TO THE NORTH. ALONG-TRACK SPREAD AT TAU 96 IS OVER 900 NM, AS SOME MODELS INDICATE DISSIPATION PRIOR TO THE COMPLETION OF THE SUBTROPICAL TRANSITION. INTENSITY GUIDANCE IS IN GOOD AGREEMENT, WITH ALL CONSENSUS MEMBERS FORECASTING SLIGHT INTENSIFICATION OVER THE NEXT 12-24 HOURS, FOLLOWED BY CONSISTENT WEAKENING AFTERWARDS. UNCERTAINTY INCREASES TOWARD THE END OF THE FORECAST PERIOD, AS SOME HAFS PROJECTS DISSIPATION AS EARLY AS TAU 60, WHILE GFS REMAINS ABOVE WARNING CRITERIA AT LEAST THROUGH TAU 84. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN